Year	Number
1991	12.55891
1997	17.47843
1998	18.10824
2001	15.20981
2002	11.84748
2003	13.12695
2006	17.28047
2008	16.36794
2014	15.8981
2015	16.26121
2016	17.12767
2017	16.6358